What is the maximum percentage of bacteriological samples that can be positive before a system violates drinking water standards?

In the context of drinking water standards, the maximum percentage of bacteriological samples that can be positive, without violating the standards, is set at 5%. This figure is crucial for maintaining water quality and ensuring public health. The 5% threshold is based on regulatory guidelines, which stipulate that if more than this percentage of samples in a given monitoring period test positive for coliform bacteria, the water system is considered to be in violation of safety standards. This benchmark serves as a protective measure against potential health risks associated with microbial contaminants in drinking water.

Understanding why this percentage is carefully defined helps water operators monitor and manage water quality effectively. Remaining under this threshold indicates that the water supply is generally safe for consumption, while exceeding it necessitates immediate corrective actions to ensure the public's safety.